Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which an additive manufacturing device forms successive layers of the part on top of previously deposited layers. Some of these technologies use extruder heads that soften or melt extrusion material, such as ABS plastic, into thermoplastic material and then emit the thermoplastic material in a predetermined pattern. The printer typically operates the extruder head to form successive layers of the thermoplastic material that form a three-dimensional printed object with a variety of shapes and structures. After each layer of the three-dimensional printed object is formed, the thermoplastic material cools and hardens to bond the layer to an underlying layer of the three-dimensional printed object. This additive manufacturing method is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
The thermoplastic material is stored in a manifold in the extruder head. The amount of thermoplastic material emitted by the one or more nozzles in the extruder head varies during production of an object. These variations are caused by the number of nozzles in the extruder head, the rate at which the extruder head and object supporting surface move relative to one another, the area of an object being formed, the temperature of the material, and the like. The fluctuating flow rate of thermoplastic material in the manifold affects the pressure of the material for its delivery through the nozzle or nozzles. A pressure within a suitable range would be preferred to enable each nozzle to emit a properly formed stream of the material. An extruder head that maintains a pressure in the manifold within a predetermined range during extrusion of the thermoplastic material would be beneficial.